Mouth Ulcers: Causes, Treatment and When to See Your Dentist

For most people, a mouth ulcer means a week or two of careful eating, and then it’s gone. For others, they keep coming back — sometimes before the last one has fully healed.

Either way, understanding what’s behind them makes them easier to manage and helps identify when one needs professional attention.

What Are Mouth Ulcers?

Mouth ulcers are small open sores that form on the soft tissue inside the mouth — the inner cheeks, gums, tongue, or lips. They’re typically round or oval, with a white or yellow centre and a red border, and most resolve on their own within 1 to 2 weeks without scarring.

The most common type is the aphthous ulcer, also called a canker sore. A virus doesn’t cause mouth ulcers, so you can’t catch them or pass them on. Cold sores are different—they appear on the outside of the lips, are caused by the herpes simplex virus, and can spread through contact.

Minor aphthous ulcers are small and usually appear one at a time, healing without treatment.

Major aphthous ulcers are less common, larger, and take longer to resolve — sometimes several weeks.

What Causes Mouth Ulcers?

Minor injury

Biting the cheek, catching the gum with a toothbrush, or irritation from a sharp tooth edge or dental appliance are straightforward physical triggers. The ulcer appears within a day or two and heals once the irritation is removed.

Acidic and spicy foods

Citrus fruits, tomatoes, pineapple, and spicy foods can trigger ulcers in susceptible people and worsen existing ones. Toothpastes containing sodium lauryl sulphate have also been associated with increased frequency in some patients.

Stress

Ulcers appear more often during periods of stress, illness, or disrupted sleep. The connection is well documented even if the precise mechanism isn’t fully understood.

Nutritional deficiencies

Low B12, iron, or folate levels are among the more overlooked causes of recurring ulcers. If they keep returning without a clear trigger, a blood test is worth discussing with a GP.

Hormonal changes

Some people — particularly women — notice ulcers following a pattern tied to the menstrual cycle. They’re also more common during pregnancy as hormone levels shift.

Medicines

NSAIDs, beta-blockers, and some chemotherapy agents list mouth ulcers as a known side effect. If ulcers develop or become more frequent after starting a new medicine, flag it to the prescribing doctor rather than managing them indefinitely at home.

What They Look Like and What to Expect

A typical ulcer begins as a tingling or burning sensation, develops into an open sore within a day, then heals gradually from the edges inward. Pain is usually sharpest in the first two to three days and eases as the ulcer closes.

Most minor ulcers resolve within seven to fourteen days. Getting several small ulcers at once rather than a single sore is common and not a sign of anything more serious.

Major ulcers take longer — sometimes several weeks — and may leave a faint scar once resolved.

Home Care

No home treatment can close an ulcer overnight, but these measures help with comfort and keep the area clean as healing progresses.

Saltwater rinse

Rinse with warm water several times daily, dissolving ½ teaspoon of salt in it. Reduces inflammation and discourages bacterial activity around the sore.

Over-the-counter gels and pastes

Topical anaesthetic gels containing benzocaine or lidocaine numb the area temporarily. Barrier pastes form a protective layer over the ulcer and reduce irritation from food and saliva. Both are available at pharmacies without a prescription.

Avoid triggers

Acidic, spicy, and crunchy foods aggravate ulcers and slow healing. Soft, neutral foods are easier to manage while an ulcer is present. If a specific food consistently triggers ulcers, cutting it out is a straightforward step worth trying.

Toothpaste

Switching to a toothpaste without sodium lauryl sulphate may reduce the frequency of ulcers in patients prone to recurrence. You can find these at most pharmacies and health food stores.

What to avoid

Don’t scrub or burst the ulcer — it delays healing and increases the risk of infection. Alcohol-based mouthwashes irritate the tissue further and should be avoided until the ulcer has resolved.

When to See a Dentist

Most ulcers clear without professional intervention. Book an appointment if:

• An ulcer hasn’t healed after three weeks
• It’s larger than a centimetre
• Ulcers are recurring frequently with little gap between episodes
• Multiple ulcers are appearing at the same time regularly
• The ulcer is accompanied by fever, swollen lymph nodes, or difficulty swallowing
• A sore is painless — less typical and worth assessing
• A sore bleeds without contact, has an irregular border, or sits on the floor of the mouth or under the tongue

If you have a sore in an unusual spot or one that doesn’t seem like a typical mouth ulcer, it’s important to have it checked by a dentist to rule out other conditions, including oral cancer.

Frequently Asked Questions

Are mouth ulcers contagious?

No. Aphthous ulcers are not viral and can’t be passed on through contact. Cold sores are contagious, but they appear on the outer lip rather than inside the mouth. If you’re unsure which you have, a dentist can clarify quickly.

Why do I keep getting mouth ulcers?

Recurring ulcers are usually linked to stress, diet, hormonal changes, nutritional deficiencies, or medicine side effects. Checking B12, iron, and folate is a useful starting point if there’s no obvious trigger. If a medicine is the likely cause, discuss it with the prescribing doctor — there may be an alternative.

How long should a mouth ulcer take to heal?

Minor ulcers typically resolve within seven to fourteen days. Major ulcers can take several weeks. Any ulcer still present at three weeks should be professionally assessed.

Can children get mouth ulcers?

Yes — they’re common in children and teenagers. Causes and home management are the same as for adults. Frequent or unusually large ulcers in children are worth raising at a dental check-up.

Is there anything that prevents them?

No guaranteed prevention. Identifying and avoiding personal triggers — specific foods, toothpaste ingredients, stress — reduces frequency for many people. Keeping B12, iron, and folate adequate helps where deficiency is a contributing factor.

Mouth Ulcers Treatment in Yeronga

If you have a mouth ulcer that hasn’t healed after three weeks, keeps coming back, or doesn’t look like a typical ulcer, get it assessed.

At Ria Family Dental, we welcome patients from Yeronga and the surrounding areas of Annerley, Fairfield, Moorooka, and Tarragindi.

Call us on 0451 359 356 or book online.

You’ll find us at 451 Fairfield Rd, Yeronga.